Detector



March 24, 1964 FlESER 3,126,522

DIRECTIONALLY SELECTIVE TRAFFIC LANE CONTROL DEVICE Filed Mrch 21, 1958 s Sheets-Sheet 1 fiTafc'fioifiiEsUfiE sENsmvE DETECTOR 3 34 1-20 F I .8411 lg. w I? 23-1 37\ 47 $36 Q '6 I DETECTOR l5 CIRCUIT MAGNETIC MAGNETIC DETECTOR DETECTOR 1 I8] 23 I0 37 DETEETQR 34 CIRCUIT 4 133% mmvron.

8 {,43 ,Lsa GARLAND E. FIESER 3| 32 44 39 BY 49 4| fl C 0421/14 a I 46 r 42" 24 Attornev March 24, 1964 Filed March 21, I958 3 Sheets-Sheet 3 T z 27 DIFFERENTIAL COUNTER Two 48 OUTPUT DIRECTIONAL 49 DETIEEJCTOR Attorney I2 l4 fi 3 i 2s 277 EL B "usv.

IM L e cOuNTER l 9 i a? 48- L ELECTRIC L Il5v. DIRECTIONAL CONTROL $8 DEIgECTOR 80 a z US v. LOCAL LANE CONTROLLER, I INVENTOR. F I g GARLANDEIF/ESER United States Patent 3,126,522 DRECTIONALLY SELECTIVE TRAFFiC LANE CQNTROL DEVICE Garland E. Fieser, East Moline, Ill., assignor, by mesne assignments, to The Gamewell Company, Newton,

Mass, a corporation of Delaware Filed Mar. 21, 1958, Ser. No. 723,038 6 Claims. (Cl. 3340-69) This invention relates to directionally selective trafiic detectors useful in detecting and registering the flow of trafiic in each of two parallel directions. Particularly, the invention relates to a traffic sensing device, and associated electric detector circuit to detect and register the flow of trafiic moving in each of two parallel directions at a range of speeds from low to moderately high.

The term trafiic as used herein shall be defined as any moving vehicle or other object.

The circuit disclosed herein is especially useful in detecting the flow of fast moving vehicular trafiic over the center lane or lanes of a multi-lane highway where traflic from either direction is permitted to use the center lane or lanes alternately or at the drivers discretion.

A directionally selective detector system of the type described is particularly useful in a traffic control system of the lane control type which allocates the inside lane or lanes to inbound or outbound trafiic depending on existing or anticipated trafiic conditions. No claim is here made to the trafiic controller, but only to the directionally selective detector circuits. Claim to the principle of alloeating various lanes of a highway to dilferent directions of traffic flow as a function of traflic density is made in patent application 738,327, dated May 28, 1958, entitled Traffic Lane Control, assigned to the assignee of the present invention.

Heretofore, devices for detecting the fiow of .traflic in two directions on a highway lane have required at least four special fast acting relays to make the circuit responsive to the short duration detector circuit closures occasioned by relatively high speed traffic. One detector circuit in use today provides an output pulse for traffic moving in one direction and no output for traflic moving in the opposite direction and thus is not confronted with the problem solved by the invention.

Non-directional pressure detector pads mounted in the roadway are comprised of a rubber encased contactor approximately 7 inches wide and approximately 6 or 8 feet long. Contact closure resultitng from the passage of a vehicle moving 40 miles per hour lasts about 10 to milli- 0 seconds and is sufficient to pull in a detector relay of standard commercial manufacture.

To make a directional detector it is normal practice to install two narrow contactors in a standard detector pad so that the assembly will be compatible with existing detector frames. Narrowing the contactors reduces the duration of the time they will be closed by a passing wheel. Installing two narrow contactors in close proximity in the same pad and frame reduces the duration of the interval between closure of successive contactors by a passing wheel. The contactors are normally made 3% inches wide with a half inch separation between them.

The invention solves the problem of short contactor closure and short interval between successive contactor closures by providing an interlock circuit which allows the first detector circuit relay pulled in to remain in and hold in through closure of the second contactor. The invention also provides two output channels, one closed during passage of a vehicle Wheel in one direction, the other closed during passage of a vehicle wheel in the op posite direction.

The invention may be used equally advantageously with 3,126,522 Patented Mar. 24, 1964 magnetic type tramc detectors and detector amplifiers. Two magnetic detectors are mounted in a highway lane in close succession and their leads connected to two detector amplifiers. Each amplifier closes an output circuit during passage of a vehicle. The circuit of the invention is connected to the output circuits of the detector amplifiers and is designed to close one output channel for each vehicle moving in one direction and another output channel for each vehicle moving in the opposite direction.

The invention may be employed equally well by building it into the detector amplifier units. The standard amplifier unit contains an output relay which is energized during the passage of a vehicle and which closes an output circuit. An extra set of interlock contacts and an interconnecting circuit between the two amplifier units serves as the directionally selective circuit and avoids the necessity of additional relays.

It is to be noted that the pressure type detector pad closes the circuit of the invention once for each wheel of a vehicle, or twice for a two axled vehicle. The magnetic detector normally closes the circuit of the invention once for each vehicle. This difference is unimportant to most trafiic actuated controllers since the closures of the pressure type detector occur in close succession and add little time thereby. When used with a controller which re sponds also to the number of detector actuations ,a simple divide-by-two circuit or relay may be provided in the controller to match it with the type of detector used. Once the controller and detector combination are installed and adjusted there is little chance that the type of detectors be changed. If the type of detector is changed at a later date, the divide-by-two circuit or relay may be adjusted accordingly.

In its simplest form the invention is useful as a device which registers the flow of traffic in both directions and signals a trafiic lane controller which compares the flow of traflic in both directions, and allots the center lane based on this comparison.

The principal object of the invention is to provide a simple, rugged, inexpensive directional trafiic detector circuit capable of being energized in one sense and held energized during passage of a vehicle in one direction and energized in another sense and held energized during passage of a vehicle in the opposite direction.

Another object of the invention is to provide an electric circuit and components which can be used in conjunction with a pressure responsive directional detector for the purpose of indicating on one output channel the passage of a vehicle moving in one direction and on a second output channel the passage of a vehicle moving in the opposite direction.

Another object of the invention is to provide a two direction traliic detector circuit to be used in conjunction with a trafiic control system which allocates one .or more of the detected lanes to the heavier direction of traflic flow.

Another object of the invention is to provide an electric circuit to be used with two magnetic detectors and two detector amplifiers to differentiate between the flow of vehicular trafiic in each of two parallel directions, indicating on one circuit the movement of trafiic in one direction and on another circuit the movement of traiiic in the opposite direction.

Another object of the invention is to provide a two direction traliic detector system which requires the installation of only one rather than two detectors in the street thereby reducing the expense and inconvenience of installation.

Another object of the invention is to provide a two output detector system, one output for one direction of trafiic flow and another output for the other direction of traffic flow.

Another object of the invention is to provide a detector system using standard components which are well proven in service, easily obtainable, reliable, economical, and which can be installed and serviced by the average electrician.

Another object of the invention is to provide a directional detector circuit which in combination with a differential counter will register the difierence in flows of traffic in two directions over the same roadway.

Another object of the invention is to provide a detector circuit as described above which in conjunction with a differential counter and a trafiic controller will allocate the center lane to the heavier direction of traffic.

Reference will be made to the following drawings, of which 7 FIGURE 1 is a wiring diagram of the detector circuit, as used with a pressure sensitive directional detector;

FIGURE 2 is a wiring diagram of the detector circuit, as used with two magnetic detectors and amplifiers;

FIGURE 3 is a wiring diagram of the detector circuit, utilizing the internal relays of the magnetic detector amplifiers;

FIGURE 4 is a wiring diagram showing the directionally selective detector unit in combination with two electric impulse counters;

FIGURE 5 is a schematic diagram showing the directionally selective detector unit in combination with a difierential counter;

FIGURE 6 is a plan view of an application of the directionally selective detector unit in combination with a counter system and a traffic control system.

Referring to FIGURE 1, the wiring diagram of the detector circuit 10 as used with a pressure sensitive directional detector 11, the circuit includes a three element detector 11 having contacts 12, 13, 14, two low voltage relays .15, 16', each controlling two movable contact arms 17, 39, 18, 44 and associated stationary contact arms, 20, 21, 41, 22, 23, 45, a source of low voltage current 30, and output terminals 24, 25. The operation of the relays is such that a closure of contact 12 against ground plate 1.3 energizes relay through normally closed relay contacts 18, 22. The circuit includes low voltage winding 32, wire 33, solenoid coil 15, Wire 34, normally closed contact 22, movable contact 18, wire 26, contact plate 12, ground plate 13, wire 35, to ground. Relay 15 when energized opens contacts 17, and closes contacts 17, 21; Subsequent closure of contact plate 14 against ground plate 13 holds relay 15 energized through now closed contacts 1 7, 21. The circuit includes low voltage winding 32, wire 33, solenoid coil 15, wire 36, contact 21, movable contact 17, wire 27, contact plate 14, ground plate 13, wire 35, to ground. Subsequent opening of contact plate 12 upon passage of the vehicle fails to deenergize relay 15 because relay 15 is maintained through now closed contacts 17, 21. Finally, opening of contact plate 14 drops out relay 15 and returns the system to normal. During the interval that relay 15 is energized, which includes the entire time that detector v12, and then both detectors 12 and 14, and then only detector 1 4 are closed, a potential is placed on output terminal 24; said potential may be used for any of a variety of purposes. This circuit incudes low voltage winding 32, wire 33, wire 38, movable contact 39, stationary contact 41, wire 42, and output terminal 24. For some applications a different potential or zero potential on output terminal 24 may be desired. This arrangement is obtained by removing wire 38 from Wire 33 and attaching Wire 33 to any desired potential source or to ground.

The mechanism works similarly upon passage of a vehicle in the opposite direction, energizing relay 16- through wire 37, opening contacts 18, 22, closing contacts 18, 23, and placing a potential on terminal through wire 46, contacts 44, 45, wire 33, and low voltage winding 32. Winding 32 derives its power from high voltage 4 winding 31, connected to a. source of power through leads 48, 49.

The operation of the directional detector circuit 10 was explained above with the input being derived from a pressure sensitive type detector 11. The operation is quite similar when two magnetic detectors 50, 51 and two magnetic detector amplifier relay units 52,53 are used. Referring to FIGURE 2, passage of vehicle 54 over the first magnetic detector 56 distorts the lines of force of the earths magnetic field and generates a small alternating potential in the windings 55 of the detector 50. This potential is fed over wire 56 and is amplified in the magnetic detector amplifier 52 and pulls in the relay associated with and part of the amplifier unit 52. Such an amplifier unit is disclosed in United States Patent Number 2,861,137, issued to George Donald Hendricks, November 18, 1958. The relay closes a circuit, usually to ground, in the same manner as a vehicle closes a circuit through contact plate 12 to ground plate 13, in FIGURE 1. The operation of the directional detector circuit 10 is the same as outlined above. That is, wire 26 being closed to ground potential allows relay 15 to become energized, opening contacts 17, 20, closing contacts 17, 21 and placing a potential on output terminal 24. The circuit includes low voltage source 32, wire 33, solenoid coil 15, wire 34, normally closed contact 22, movable contact 18, wire 26, relay part of amplifier unit 52, to ground.

Continued passage of vehicle 54 results in the further distortion of the earths magnetic field through the windings 57 of the second magnetic detector 51. A small potential is generated in the windings 57 of the detector; this potential is fed over wire 58 and is amplified in the magnetic detector amplifier 53 and pulls in the relay associated with and part of amplifier unit 53. The relay closes a circuit to ground, in the same manner as a vehicle closes a circuit through contact plate 1 4 to ground plate 13, in FIGURE 1. The wire 27 being closed to ground potential holds relay 15 energized through now closed contacts 17, 21. Relay 16 is not energized because contacts 17, 20 are open. The circuit includes low voltage source 32, wire 33, solenoid coil 15, wire 36, stationary contact 21, movable contact 17, wire 27, relay part of amplifier unit 53, to ground. Subsequent opening of the relay, a part of magnetic amplifier 52, has no effect on the detector circuit 10; relay .15 remains energized through its own holding contact 21. Upon completion of passage of the vehicle 54, the relay associated with and part of magnetic amplifier 53 opens, deenergizing relay 1-5, returning the circuit to normal. During the interval relay 15 is energized, a potential is placed on output terminal 24 which potential may be used for a variety of purposes, as hereinafter-described.

While the invention has been described as a separate and individual apparatus utilizing the output of two magnetic detector amplifier units, the invention may be incorporated into the amplifiers with only minor change and at low cost. To further reduce the cost, future amplifier units may be constructed with the required additional relay contacts supplied within the unit.

Referring now to FIGURE 3, the output relays 15, 16 in present or future amplifier units 62, 63 could be equipped with the interlock contacts 17, 20, 21,18, 22, 23. With a simple two wire interconnection 34, 47 between amplifier units 62, 63 the invention could be constructed with a very minimum of apparatus. Thus, any two detector amplifier units 62, "63 equipped with the extra relay contacts 17, 20, 21, 18, 22, 23 could be connected to provide output at two output circuits 24, 25, one for each direction of travel.

Passage of vehicle 54 over the first magnetic detector 50 distorts the lines of force of the earths magnetic field and generates a small alternating potential in the windings 55 of the detector 50. 'This potential is fed over wire 56, wire 26, movable contact 18, normally closed contact 22, wire 34, to amplifier 60. The potential is amplified in amplifier 6t and energizes relay 15 which closes movable contact 17 to stationary contact 21, and opens contacts .17, 2d. Relay 15 also closes movable contact 39 to stationary contact '41, energizing output terminal 24 from any desired source over wire 3-8. The output may be used for a number of purposes to be described hereinafter.

Continued passage of vehicle 54 results in further distortion of the earths magnetic field through the windings 57 of the second magnetic detector 51. A small potential is generated in the windings 57 of the detector 51. This potential is fed over wire 58, wire 27, movable contact arm 17, contact 21, wire 36, and into amplifier 60, where it tends to sustain the output voltage and maintain relay l5 energized.

Further passage of vehicle 54 permits the restoration of the magnetic field through the windings 55 of the first magnetic detector 51. The small potential generated in the windings 55 reduces to Zero and this change continues to be amplified by amplifier 6t) and continues to hold in relay 15. While winding 55 has stopped generating, winding 57 still continues to generate a small potential, depending upon the speed of vehicle 54 and the distance between detectors 5d, 51. This output continues over wire 53, wire 27, contacts 17, 21, wire 36 to amplifier dd, and amplified, sustains relay 15.

Upon completion of passage of vehicle 54, no further potential is generated, causing amplifier 60 to reduce its output to zero, resulting in the deenergization of relay 15. Relay contacts T7, 21, and 39, 41 opens, disconnecting output terminal 24 from its source.

Passage of a vehicle over detectors 5t), 51 in the opposite direction results in the operation of amplifier 61 which switches any desired source to output terminal 25. :For this reason the apparatus is termed a two output directional detector.

One use for the two output directional detector circuit is in conjunction with two electrically operated impulse counters 7tl, 71 for determining the flow of vehicular traific over one common lane 8 of a highway 9, as shown in FIGURE 4.

The output resulting from the passage of a vehicle 54 in one direction is recorded on one counter '76); the output resulting from the passage of a vehicle 7 in the opposite direction over the same roadway 8 is recorded on a second counter 71. The former circuit includes output terminal 24, wire 75, counter coil 72, to ground. Of course, a power supply could be connected to counter coil 72 so that output terminal 24 could be switched to ground potential by relay llS. Counters '70, 71 may have a readout circuit 75', 77.

The sums noted on the counters 7d, 71 comprise information for a trafiic study, or may be utilized through electric readout circuits to relay information to a remote central control location, or may be utilized in combination with an actuated traffic controller of the lane control type described in patent application 73 8,327 to control the fiow of trafiic on a multi-lane roadway, as shown in FIGURE 6.

In one embodiment, the invention is used in conjunction with an electric impulse counter 78 of the add and subtract or differential type as shown in FIGURE 5. One example of such a counter is shown in patent application 799,363, filed March 1-3, 1959, entitled Electric Differential Counter, assigned to the assignee of the present invention. In this embodiment, it is desired to ltnow only the difference in the flow of traffic in two directions over the same roadway 8. The add circuit "includes output terminal 24, wire 75, add solenoid coil '72, to ground. The subtract circuit includes output terminal 25, wire 74, subtract solenoid coil 73, to ground. The electric impulse counter 78 may be of the reset type, which totals the difference of fiow over a timed period, and resets to Zero upon receipt of a reset impulse from a timer. This would permit the measurement of traflic density which is the measure of traffic flow per unit of time.

In another embodiment, the directionally selective traffic detector is used in conjunction with standard pressure sensitive detectors in all lanes in which traflic may move in only one direction. Referring to FIGURE 6, directional detector 11 is employed in the center lane 8. Standard detectors 5, 6 are employed in the outside lanes of highway h.

A two output directional detector 10 is used in conjunction with a directional detector .11. The output 24 for one direction of trafific is combined with the output of the detector 6 and is fed to electric impulse counter 80. The output 25 for the opposite direction of traffic is combined with the output of the detector '5 and is fed to a second electric impulse counter '81.

Electric impulse counters 8t 81 are arranged to turn a potentiometer shaft such that their voltage output is substantially proportional to the count registered. The voltage outputs of the two potentiometers are fed to a lane selector 82 of the type disclosed in United States patent application 738,327, filed May 28, .1958, entitled Traiiic Lane Control.

The lane control 82 weighs the two potentials and switches the higher potential to a Voltage divider network within .the lane control. The voltage divider is settable to obtain various ratios. The lane control then compares the lower potential with the higher potential reduced by a preset ratio. If the higher potential reduced by the preset ratio is still higher than the lower potential, the lane control energizes a line 83 or '84 to the local lane controller 85 which switches the lane signals 8 d, 87 to favor the heavier direction of trafiic fiow. If the lower potential is higher than the reduced higher potential, the lane control 82 retains the normal display of signals 85, 87.

Thus, when the difference in rates of trafiic flow exceed the predetermined ratio, the lane allocating system be comes effective. The local lane controller 85 changes the traffic signals from flashing amber to steady amber, indicating to motorists that a traflic change is occurring. Which direction of traffic flow receives the green signal is determined by the counter with the larger count. The local lane controller $5 allots the green signal over the center lane to the heavier direction of flow.

The system remains in this state for at least a preset time interval, depending upon traffic conditions on the highway. At the beginning of each interval, the two counters 80, 81 are reset to zero and resume counting trafiic. if, at the end of the predetermined time interval, traific conditions warrant a reallocation of the center lane to traffic from the opposite direction, a traflic change indication will be given with steady amber lights. Subsequently, the signal lights 85, 87 over the center lane will change, giving the green signal to the opposite direction of traidc. It will be understood that traific changes Will be made infrequently (possibly ten times per 24 hour period) although trafiic sampling intervals will be relatively short (possibly *five minutes). The reason for this is that traffic on a highway on which this system will normally be applied follows a fairly definite and simple pattern: heavy inbound traffic in the morning hours, dispersed traific during the day, heavy outbound trafiic during the late afternoon, dispersed traffic during the evening, and light trafiic at night.

It will be understood by one skilled in the art of traffic control that, although the traflic signal indications over the center lane are not controlled by local trailic controllers at intersections along the highway, the motorist will first obey the signals at each signalized intersection. Experience has shown that when the motorist sees a green signal over the center lane or lanes, and a red signal at the intersection signal, he will obey the intersection signal and stop.

shaasa a The circuit of the invention is designed to operate reliably on impulse of short duration using fast acting relays of standard manufacture. Standard relays are able to operate under these conditions because of the overlapping nature of the detector contact closures and the design of the interlocking circuit. Closure of the first detector contact serves to energize the first relay which switches a holding circuit to stand ready for closure of thesecond detector contact. Closure of the second detector contact overlaps the closure of the first detector contact and sustains the relay. Opening of the first detector contact has no eflect on the energization of the relay because it is maintained energized by the second detector contact. Opening of the second detector contact deenergizes the relay and it drops out. Operation of the detector in reverse order causes a second relay to pull in, hold in, and drop out in identical manner. While one or the other relay is energized it closes a pair of contacts in one or the other output channels and supplies signal to a counter, recorder, controller, or computer.

It will be understood that the forms of the invention as herein described do not constitute the only forms the invention may take. The invention is not limited to the forms used here by Way of illustration.

I claim:

1. In a traffic registering and counting system, a traflic detector in each exclusively inbound trafiic lane, a traffic detector in each exclusively outbound traffic lane, a twodirection trafiic detector in each lane used during one period for inbound trafiic and during another period for outbound traffic, two counters, one associated with each direction of traffic, a source of power, an electric circuit connecting the outputs of all inbound detectors to one of said counters and another electric circuit connecting the outputs of all outbound detectors to the other of said counters.

2. In a master trafiic control system, a uni-directional trafiic detector in each lane in which trafiic moves in one direction, a dual directional traffic detector in each lane in which traflic may move in one direction at one time and the opposite direction at another time, a directionally selective trafilc detector circuit for each dual-directional detector, a first and second traffic counter, said first counter connected to said detectors and to said directionally selective trafiic detector circuits for counting the trafiic moving in one direction per unit of time, said second trafiic counter connected to said detectors and to said directionally selective trafiic detector circuits for counting the tratfic moving in the opposite direction per unit of time, discriminator means for comparing the totals reached by said first and second counters at the end of said time unit and for allocating the center lane or lanes to the heavier direction of trafiic flow, and timed reset means on said counters to remove the total therefrom at the end of said unit time.

3. In a master trafiic control system, a highway comprised of lanes; a trafiic detector in each highway lane, first and second traflic counters, said first counter connected to all of said detectors over which traffic is moving in one direction for counting such trafiic per unit of time, said second counter connected to all of said detectors over which trafiic is moving in the other direction for counting such trafiic per unit of time, discrimi nator means for comparing the totals on said first and second counters at the end of each time unit and for allocating the center lane or lanes to the heavier direction of traffic EfiOW, timed reset means to remove the totals from said counters at the end of said time unit, and electric switching means to connect said detector in the allocated lanes to the counter for the same direction of trafiic flow.

4. A dual direction detector circuit for use with two magnetic detectors and two magnetic detector amplifiers connected each with one of said detectors, said circuit H c 8 including in combination first and second switching means each controlled by one of said amplifiers and having an energized condition and a de-energized condition; one of said amplifiers and one of said detectors interconnected when said first switching means is in said 'de-energized condition, the other of said detectors also connected to said one amplifier when said second switching means is in said energized condition, said one amplifier thereby connected to receive the output of first one and then the other of said detectors and to energize said second switching means concurrently, and a second output means closed when said second switching means is in said energized condition, said second switching means when in said deenerg-ized condition for connecting the other of said detectors to the other of said amplifiers, said switching means when in said energized condition for connecting said one of said detectors also to said other of said amplifiers, said amplifier thereby connected to receive the output of first one and then the other of said detectors and to energize said first switching means concurrently, and a first output means closed when said first switching means is energized.

5. A directional magnetic detector for discriminating between each of two opposite directions of traffic movement and adapted tor application with two magnetic detectors disposed in spaced apart relationship in the same lane, and including two magnetic detector amplifiers, connected one to the input circuit of its respective detector, said two direction detector circuit comprising first and second relays, each said relay having a coil, a set of double throw contacts and a set of normally open contacts, a source of potential, said coil of said first relay connected to said source of potential and to a normally open contact of said double throw contacts on said first relay and to a normally closed contact of said double throw contacts on said second relay, said coil of saidsecond relay connected to said source of potential and to a normally open contact of said double throw contacts on said second relay and to a normally closed contact of said double throw contacts on said first relay, a movable contact of said double throw contacts on said first relay connected to said output circuit of one of said amplifiers, a movable contact of said double throw contacts on said second relay connected to said output circuit of the other of said amplifiers, one contact of each of said set of normally open contacts connected to said source of power, a first output terminal connected to the other contact of said set of normally open contacts on said first relay, a second output terminal connected to the other contact of said set of normally open contacts on said second relay, said first output terminal energized when traffic moves over said detectors in one direction, and said second output terminal energized when tratfic moves over said detectors in an opposite direction.

6. A directional magnetic detector adapted for discriminating between each of two opposite directions of trafiic movement and adapted for application with two magnetic detectors disposed in spaced apart relationship in the same lane and including two magnetic detector amplifiers, two detector units disposed sequentially in the same traific path and connected one to each of said amplifiers, said circuit including a first and a second relay each associated with a respective .one of the amplifiers, each of said relays having a coil and a set of transfer contacts consisting of a normally open contact, a normally closed contact and a transfer contact and also having a pair of contacts consisting of an output contact and a movable contact, each of said amplifiers having an input terminal and an output terminal, means forming two interconnecting circuits between said amplifiers, an output circuit one from each amplifier, one of said interconnecting circuits including one of said detectors, said transfer contact on said first relay and said normally closed contact on said first relay; the other of said interconnecting circuits including the other of said detectors, said transfer contact References Cited in the file of this patent UNITED STATES PATENTS 1,410,292 Granstrom Mar. 21, 1922 19 Hershey June 16, Crago Apr. 26, Logan May 15, Carr Mar. 9, Geer Apr. 20, Horni May 27, Cooper Dec. 11, Barker Apr. 29,

FOREIGN PATENTS Great Britain Oct. 30, Great Britain Sept. 14, France Oct. 15, 

3. IN A MASTER TRAFFIC CONTROL SYSTEM, A HIGHWAY COMPRISED OF LANES; A TRAFFIC DETECTOR IN EACH HIGHWAY LANE, FIRST AND SECOND TRAFFIC COUNTERS, SAID FIRST COUNTER CONNECTED TO ALL OF SAID DETECTORS OVER WHICH TRAFFIC IS MOVING IN ONE DIRECTION FOR COUNTING SUCH TRAFFIC PER UNIT OF TIME, SAID SECOND COUNTER CONNECTED TO ALL OF SAID DETECTORS OVER WHICH TRAFFIC IS MOVING IN THE OTHER DIREC-----TION FOR COUNTING SUCH TRAFFIC PER UNIT OF TIME, DISCRIMINATOR MEANS FOR COMPARING THE TOTALS ON SAID FIRST AND SECOND COUNTERS AT THE END OF EACH TIME UNIT AND FOR ALLOCATING THE CENTER LANE OR LANES TO THE HEAVIER DIRECTION OF TRAFFIC FLOW, TIMED RESET MEANS TO REMOVE THE TOTALS 